External ambulatory infusion devices for the infusion of a liquid drug over an extended time period may be used for a number of therapies. In particular, such devices form the basis for a therapy of Diabetes Mellitus by CSII (Continuous Subcutaneous Insulin Infusion). An ambulatory infusion device is designed to provide a basal drug supply substantially continuously night and day in accordance with a time-variable basal infusion schedule and is further designed to administer larger drug boli in a short time period on demand. The device is typically designed to be carried substantially continuously over an extended time period of typically several months up to several years.
In the following, an external ambulatory infusion device according to the technical field as stated above and in particular an ambulatory infusion device in accordance with the present disclosure is referred to as “device”. Besides diabetes therapy, those devices may be used for a number of further therapies, such as cancer treatment or pain therapy, without requiring substantial modification.
Such devices are typically powered by one or multiple energy storages, in particular rechargeable or non-rechargeable batteries. Several single batteries may typically be connected in series, thus forming an overall battery of higher voltage. Alternatively or additionally, several batteries may be provided for dedicated purposes, such as one battery for powering the device under normal conditions and another battery as safety backup; one battery for powering the electronics and another one for powering the pump drive, or the like. In such configurations, the present disclosure may be applied to any or all of those different batteries.
Many existing ambulatory infusion devices are designed to repeatedly carry out a battery test. In such a battery test, the battery is connected to a test load for a short time period and the resulting terminal voltage is measured. In the following, a test load is generally assumed to be an Ohmic resistor, but it may also be complex, having an inductive and/or capacitive component. An alert is generated if the measured voltage is below a given threshold voltage. The testing interval between consecutive tests is typically in the range of some minutes.